pajero4us - I can reccomend !Xaus Lodge for your 50th birthday. I have been there 3 times already and once stayed for 2 nights and the other times only for a night.
Yes it is a different experience to the other camps in KTP, but you experience the Kalahari in another wonderful facet. We were "fortunate" to be there with only one or 2 other huts occupied (on all 3 occasions) - which made these visits all the more tranquil and special. The Sundowner drive, Night drive and the morning walks in the veld all adds to this. The staff are friendly and down to earth and the food, views and accomodation awesome.
I see this as a must visit if you can (prices are very steep - think R 2000 pppn) - also look out for specials and it doesn't cost you anything to ask them for a better deal (which worked for us

last time around)
I personally would not stay there for more than 2 nights as I have a little bit of ADD - but I would if at all possible always go back.